Cholesterol has been known for many years to be a component of atherosclerotic plaques. Mounting evidence indicates diets high in cholesterol may increase the levels of cholesterol in the blood which, in turn, increase the risk of atherosclerotic disease and its attendant manifestations of heart attack, stroke and other tissue injuries resulting from atherosclerosis. Cholesterol absorbed from dietary sources is thought to increase the risk of atherosclerotic disease.
Other than avoidance or reduced consumption of high cholesterol foods, measures available without prescription to the general public to reduce the absorption of cholesterol from the diet have met with little success. However, high cholesterol levels in serum can be lowered effectively by altering the intestinal metabolism of lipids. In recent years, it has become known that certain plant sterols and plant stanols such as .beta.-sitosterol (24-ethyl-5-cholestene-3.beta.-ol) and its hydrogenated form .beta.-sitostanol (24-ethyl-5.alpha.-cholestane-3.beta.-ol) can help lower serum cholesterol by inhibiting cholesterol absorption. Plant stanols are the hydrogenated form of plant sterols. See, e.g., "Reduction of Serum Cholesterol With Sitostanol-ester Margarine in a Mildly Hypercholesterolemic Population", New England Journal of Medicine, Nov. 16, 1995, pp. 1308-1312.
For purposes of this invention, "plant sterols" is intended to include both plant sterols and plant stanols; the term "sterols" alone is intended to include only the plant sterols; and the term "stanols" alone is intended to include only the plant stanols. Likewise, for purposes of this invention, "plant sterol esters" is intended to include both plant sterol esters and plant stanol esters; the term "sterol esters" alone is intended to include only the plant sterol esters; and the term "stanol esters" alone is intended to include only the plant stanol esters. For purposes of this disclosure, a "cholesterol-reducing-compound" is defined as either a plant sterol or a plant sterol ester as defined herein.
For purposes of this invention, "emulsifier mixture" is intended to include one of three different possible emulsifier mixtures: (1) a mixture of emulsifier A which has an HLB ranging from about 6 to about 9, emulsifier B which has an HLB ranging from about 2 to about 6, and emulsifier C which has an HLB ranging from about 9 to about 22; (2) a mixture of emulsifier A which has an HLB ranging from about 6 to about 9 and emulsifier C which has an HLB ranging from about 9 to about 22; and (3) a mixture of emulsifier B which has an HLB ranging from about 2 to about 6 and emulsifier C which has an HLB ranging from about 9 to about 22.
The use of plant sterols in food products is considered safe, since plant sterols are natural components of vegetable fats and oils. Plant sterols themselves are not absorbed--or only absorbed in very small amounts--from the intestines. A decreased incidence of coronary disease is clearly associated with a decrease in serum cholesterol and, in particular, a decrease in LDL cholesterol. A high serum cholesterol value is one of the most significant indicators of risk of coronary disease. There are a variety of naturally occurring plant sterols which have been reported to have a cholesterol-reducing effect, although not all have equivalent action. The mechanism by which plant sterols achieve this effect has not been fully elucidated.
In recent years, many efforts have been made to reduce the fat content of various foods, such as salad dressing, sour cream and frozen desserts. When the fat level is reduced in conventional food products, however, the organoleptic properties are generally adversely affected because of the oiliness (lubricity) and slipperiness imparted by the fat particles suspended in the food product are effectively lost.
Other mouthfeel and textural properties such as richness and creaminess may also be adversely affected by removal or reduction of fat. Polysaccharide and protein ingredients commonly known as fat mimetics have been used to restore some of the textural properties contributed by emulsified fats and oils, such as viscosity and gel strength. They have been used less successfully to restore more subtle mouthfeel factors. In addition, many of these ingredients have negative impact on flavor, another key aspect of product quality. The FDA Standards of Identity recognize "reduced-fat" foods as foods that have 25% less fat than the market standard of a full-fat counterpart of that food type. "Light" products retain 50% less fat than the market standard of a full-fat serving of that food type. "Low-fat" foods are defined as having less than 3 grams of fat per serving, and "fat-free" foods have less than 1/2 gram fat per serving.
For purposes of this invention, the term "low-fat" includes "reduced-fat," "light," "low-fat," and "fat-free" as defined by the FDA Standards of Identity. In addition, for purposes of this invention, "low-fat" also encompasses triglyceride-free products although they are not included in the FDA Standards of Identity. However, the term "fat-free" is intended to include only "fat-free" as defined by the FDA Standards of Identity. In addition, the terms "low-fat" and "fat-free" are intended to include low-fat and fat-free food products that do not fall into the categories defined by the FDA Standards of Identity (as of the time of this disclosure) but deliver to the consumer reduced levels of fat per serving. Furthermore, through the use of higher levels of plant sterol esters, even if no oil is added in a formulation of the described compositions, while such a composition may not be termed "fat-free", the term "triglyceride-free" is an accurate description of such formulations utilized in this disclosure.
Low-fat and fat-free food products have been developed which duplicate the viscosity and other textural attributes of the missing fat by means of suitable food polymers, such as gums (xanthan or alginate), cellulose and its derivatives, starches and various microparticulated polymeric complexes. Unfortunately, such additives generally cannot provide the desired organoleptic characteristics normally associated with full-fat products, namely flavor, mouthfeel and thermal factors.
Many of these desired attributes associated with full-fat products are due to the presence of two distinct phases--an aqueous phase and an oil phase. The oil phase provides a reservoir of solvent for the flavor chemicals to dissolve in. By altering the proportions of the two phases, the partitioning of the flavor chemicals between the two phases is changed, affecting the character of the flavor and the way it is released in the mouth. In the extreme example of a fat-free product, the product consists of a single phase, and the flavor chemicals are dispersed in the aqueous phase. Free oil typically contributes to the mouthfeel of full-fat products. In the mouth, some free oil separates from the bulk of the product, coats the mouth, and provides oily lubricity. Fats and oils also contribute thermal sensations in the mouth. These effects can be either mouthwarming as a result of the coating of the free oil, or mouthcooling due to melting of any crystalline fat.
The cholesterol-reducing-compound-containing mesophase-stabilized compositions which are provided by the present disclosure significantly improve the quality of low-fat and fat-free food products by providing some of the aforementioned missing attributes. They do this by providing a separate phase, a mesophase, which is neither an aqueous phase nor an oil phase, but a liquid crystalline phase of both hydrophobic and hydrophilic character. They also provide a way of potentiating or maximizing the oily and fatty attributes of whatever oils or fats exist in the low-fat or fat-free product. By light microscopy, the mesophase-stabilized emulsions contain oil droplets which appear in a narrow range of sizes as relatively small-sized oil droplets dispersed in an aqueous gel phase. Upon centrifugation, most of the mesophase-stabilized emulsions of the present invention separate into an oil emulsion and a mesophase gel. In a food product, the oil droplets of the emulsion phase release their oil, providing lubricity, flavor delivery, and mouthwarming.
The mesophase gel provides stability and structure to the food product. Because starch components and other stabilizing or thickening agents are not required to structure the food product, maximum oily mouthfeel and flavor characteristics are retained. In fact, any fats or oils present in the mesophase-stabilized emulsions or mesophase-stabilized dispersions are potentiated by the present invention. The present invention represents a new method for introducing plant sterols and plant sterol esters into low-fat and fat-free food products by allowing highly viscous emulsions and dispersions to be made regardless of the oil level, with no requirement for polymeric protein or polysaccharide thickening or bulking ingredients. Additionally, the compositions of the present invention permit the introduction of cholesterol-reducing compounds into the diet in a highly effective manner.
Conventionally, plant sterols have been incorporated into food products by melting a sterol or stanol, incorporating it into an oil phase, and blending the oil phase with other components to result in a plant sterol-containing food product. However, the plant sterols have high melting points, about 100-180.degree. C., which result in the crystallization of the plant sterols within the oil phase of such food products. Such crystallization of the plant sterols within the oil phase results in a gritty texture attributed to the food product into which the oil/plant sterol phase is incorporated. This gritty texture is especially detectable when the oil/plant sterol phase is incorporated at high levels in the food products. However, esterification of plant sterols results in lower melting points of the plant sterol esters, usually about 16.degree. C. to about 90.degree. C. Thus, the plant sterol esters are less likely to crystallize during manufacture of food products and are, therefore, the more preferred form of the cholesterol-reducing agents. However, most plant sterol esters will crystallize in the food product unless their melting point is below the storage temperature of the food product into which they are incorporated. Although the use of plant sterol esters allows for improved incorporation in food products (as compared to the plant sterols with higher melting temperatures), it would still be desirable to have alternative methods of incorporating plant sterols and/or plant sterol esters into low-fat and fat-free food products. The present invention provides such methods.
This invention uses mesophase-stabilized compositions to incorporate plant sterols and/or plant sterol esters in a variety of food products. By incorporating the plant sterols and/or plant sterol esters into low-fat and fat-free food products by use of a mesophase, the cholesterol-reducing-compounds are effectively dispersed as individual molecules in the mesophase structure and thus reduce the tendency to crystallize. Moreover, since the plant sterols and/or plant sterol esters form an integral part of the mesophase structure, it is not necessary to incorporate them into food products by using an oil carrier. Any excess (i.e., any that is not dispersed into the mesophase) plant sterols or plant sterol esters can be readily dispersed as an emulsion in the mesophase by using high shear (e.g., about 5000 sec.sup.-1 to about 50,000 sec.sup.-1). Thus, the plant sterols or plant sterol esters may be incorporated as an integral part of the mesophase and/or as an emulsion stabilized by the mesophase.
This invention allows larger amounts of plant sterols and/or plant sterol esters to be incorporated in low-fat or fat-free food products without adversely affecting the organoleptic properties. In fact, the use of a mesophase to incorporate plant sterols and plant sterol esters can actually improve the organoleptic properties of the resulting food products and can result in new product concepts. Creamy mesophase-stabilized emulsions may be made with as much as 10 percent stanols, 10 percent sterols, 30 percent stanol ester, or 50 percent sterol ester. Since the plant sterols and/or plant sterol esters are incorporated without the need for an oil carrier, lower fat products can easily be created. In addition, the biological attributes of the plant sterols and/or plant sterol esters are enhanced when incorporated using the mesophase of the present invention. Since the plant sterols and plant sterol esters appear to be contained as molecular inclusions in the mesophase structure, they are delivered to the intestine in a form similar to that when cholesterol is emulsified in bile-salt micelles and delivered to the intestines. This enhanced delivery system should allow the currently recommended dosage of about 3 g/day to be achieved in an easier and more acceptable form for the consumer.
It is an object of the present disclosure to provide low-fat and fat-free food products which incorporate plant sterols and/or plant sterol esters as cholesterol-reducing agents in low-fat and fat-free foods. The cholesterol-reducing agents are incorporated into mouthfeel-enhancing, texture-building, emulsion-stabilizing and dispersion-stabilizing compositions which are mesophase-stabilized emulsions and dispersions for use in low-fat and fat-free food products. Using the present system, high levels of these agents can be used in food products without adversely affecting the organoleptic properties of the food products.
It is a further object of the present disclosure to provide methods for making low-fat and fat-free food products containing plant sterols and/or plant sterol esters as cholesterol-reducing agents. These methods generate mouthfeel-enhancing, texture-building, emulsion-stabilizing and dispersion-stabilizing compositions which are cholesterol-reducing-compound-containing mesophase-stabilized compositions for use in low-fat and fat-free food. These and other objects and advantages of the present invention will be apparent to those skilled in the art upon consideration of the present disclosure.